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Posted to dev@lucene.apache.org by George Aroush <ge...@aroush.net> on 2006/12/14 03:20:26 UTC

Locale string compare: Java vs. C#

Hi folks,

Over at Lucene.Net, I have run into a NUnit test which is failing with
Lucene.Net (C#) but is passing with Lucene (Java).  The two tests that fail
are: TestInternationalMultiSearcherSort and TestInternationalSort

After several hours of investigation, I narrowed the problem to what I
believe is a difference in the way Java and .NET implement compare.

The code in question is this method (found in FieldSortedHitQueue.java):

    public final int compare (final ScoreDoc i, final ScoreDoc j) {
        return collator.compare (index[i.doc], index[j.doc]);
    }

To demonstrate the compare problem (Java vs. .NET) I crated this simple code
both in Java and C#:

    // Java code: you get back 1 for 'res'
    String s1 = "H\u00D8T";
    String s2 = "HUT";
    Collator collator = Collator.getInstance (Locale.US);
    int diff = collator.compare(s1, s2);

    // C# code: you get back -1 for 'res'
    string s1 = "H\u00D8T";
    string s2 = "HUT";
    System.Globalization.CultureInfo locale = new
System.Globalization.CultureInfo("en-US");
    System.Globalization.CompareInfo collator = locale.CompareInfo;
    int res = collator.Compare(s1, s2);

Java will give me back a 1 while .NET gives me back -1.

So, what I am trying to figure out is who is doing the right thing?  Or am I
missing additional calls before I can compare?

My goal is to understand why the difference exist and thus based on that
understanding I can judge how serious this issue is and find a fix for it or
just document it as a language difference between Java and .NET.

Btw, this is based on Lucene 2.0 for both Java and C# Lucene.

Regards,

-- George Aroush


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Re: Locale string compare: Java vs. C#

Posted by Chuck Williams <ch...@manawiz.com>.
Surprising but it looks to me like a bug in Java's collation rules for
en-US.  According to
http://developer.mimer.com/collations/charts/UCA_latin.htm, \u00D8
(which is Latin Capital Letter O With Stroke) should be before U,
implying -1 is the correct result.  Java is returning 1 for all
strengths of the collator.  Maybe there is some other subtlety with this
character...

Chuck


George Aroush wrote on 12/13/2006 04:20 PM:
> Hi folks,
>
> Over at Lucene.Net, I have run into a NUnit test which is failing with
> Lucene.Net (C#) but is passing with Lucene (Java).  The two tests that fail
> are: TestInternationalMultiSearcherSort and TestInternationalSort
>
> After several hours of investigation, I narrowed the problem to what I
> believe is a difference in the way Java and .NET implement compare.
>
> The code in question is this method (found in FieldSortedHitQueue.java):
>
>     public final int compare (final ScoreDoc i, final ScoreDoc j) {
>         return collator.compare (index[i.doc], index[j.doc]);
>     }
>
> To demonstrate the compare problem (Java vs. .NET) I crated this simple code
> both in Java and C#:
>
>     // Java code: you get back 1 for 'res'
>     String s1 = "H\u00D8T";
>     String s2 = "HUT";
>     Collator collator = Collator.getInstance (Locale.US);
>     int diff = collator.compare(s1, s2);
>
>     // C# code: you get back -1 for 'res'
>     string s1 = "H\u00D8T";
>     string s2 = "HUT";
>     System.Globalization.CultureInfo locale = new
> System.Globalization.CultureInfo("en-US");
>     System.Globalization.CompareInfo collator = locale.CompareInfo;
>     int res = collator.Compare(s1, s2);
>
> Java will give me back a 1 while .NET gives me back -1.
>
> So, what I am trying to figure out is who is doing the right thing?  Or am I
> missing additional calls before I can compare?
>
> My goal is to understand why the difference exist and thus based on that
> understanding I can judge how serious this issue is and find a fix for it or
> just document it as a language difference between Java and .NET.
>
> Btw, this is based on Lucene 2.0 for both Java and C# Lucene.
>
> Regards,
>
> -- George Aroush
>
>
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> To unsubscribe, e-mail: java-dev-unsubscribe@lucene.apache.org
> For additional commands, e-mail: java-dev-help@lucene.apache.org
>
>   


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